An electrical system may utilize both alternating current (AC) and direct current (DC) power. For instance, a powertrain of a battery electric or hybrid electric vehicle or other torque-generating system typically includes one or more high-voltage AC electric machines, each of which is powered by a DC device such as a multi-cell battery pack or a fuel cell. An AC-DC converter is used in such a system to perform the necessary power conversion functions. For instance, a passive diode bridge and actively-controlled switching elements such as MOSFETS or IGBTs may be used to eliminate the negative cycle of an AC input waveform, with the resultant voltage output thereafter filtered to provide a DC output waveform.
In some electrical systems using an AC power supply, recharging of a DC battery pack or powering of a DC device may be achieved by plugging the electrical system into an offboard charging port, such as an available AC wall outlet or charging station. For example, an AC-DC multiconverter system may be used in certain plug-in vehicles to convert an AC input voltage from a wall outlet or charging station into a DC voltage.
120/240 VAC single phase AC is widely available in the developed world as a residential voltage supply. In such a configuration, the AC voltage supply is a “split phase” supply in which the peak voltage relative to ground is 120 VAC or 240 VAC. In some locations, however, multiphase AC power is standard, e.g., three phase voltages and currents are provided that differ from each other by a third of a cycle or 120 electrical degrees. Therefore, conventional approaches to power conversion designed for single phase applications may be less than optimal when used with multiphase AC power.